spider mites are a pita.
Spider mites are easy to identify and they sure love anything with a hint of sativa in it. Look under the effected leaves and you'l see little moving dots, their incredibly small but they do a lot of damage. Chemical solutions knock them dead instantly but about three days later the eggs will hatch a new colony of the buggers, hit them again and once more three days later again usually does the trick for me.
I had blueberry and northern lights in one grow long before the days info was this widely spread online. The NL was completely infested before I figured out what they where but the blueberry was extremely pest resilient and didn't have any signs of pests the entire grow despite being right next to each other. tried everything under the sun to get rid of those bastards trying to stay organic with no results. chemicals work well enough but plants that like to get them can be a battle to keep them gone, for those I like to give them a good blast shortly before flowering and throw the plants in the tub to spray any chemicals off the plants a week later or just before I flower just in case then try some organic solutions to ward them off for the rest of the time.